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Introduction

Current Research Topics include:
1) Determination of the potential energy surfaces (PESs) for the polyatomic molecules or weakly bound systems;
2) Exact full quantum calculation of the infrared or microwave spectra for small molecules or molecular clusters;
3) Development of Path Integral Monte-Carlo (PIMC) or Path Integral Molecular Dynamics (PIMD) methods;
4) Development of the new method to calculate 1-D, 2-D IR spectra;
5) Simulations of the microscopic superfluidity in doped quantum solution;
6) Simulations of the IR spectra of aerosol in the atmosphere.

Additional affiliations

October 2010 - present

September 2005 - September 2010

September 2002 - July 2005

## Publications

Publications (86)

The fundamental properties of molecules bridge experiment and theory. Transport properties (diffusion, thermal diffusion, thermal conductivity and viscosity) of binary mixtures are measurable in experiments, and well-defined in theory, but difficult to compute with a high accuracy. Beside high-accuracy intermolecular potential energy curves (PECs),...

The ab initio intra- and inter-molecular potential energy surfaces (PESs) for the H2O-Ne system that explicitly incorporate the intramolecular overtone state (vOH = 2) of H2O are presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory [CCSD(T)-F12] level with an augmented correlatio...

Three state-of-the-art ab initio interatomic potential energy functions (PEFs) for the Kr-Ne, Kr-Ar, Kr-Xe rare gas dimers are presented. These PEFs are based upon extrapolation to complete basis set (CBS) limit results of supermolecular computations at the coupled-cluster level with single, double, and perturbative triple excitations (CCSD(T)) and...

New interatomic potential energy curves of xenon-helium (Xe-He), xenon-neon (Xe-Ne), and xenon-argon (Xe-Ar) atom pairs are developed by state-of-the-art ab initio calculations. Coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)] is used to calculate the majority of the interaction between atoms, on (multiple)...

Vibrational spectroscopy is a useful technique for probing chemical environments. The development of models that can reproduce the spectra of nitriles and azides is valuable because these probes are uniquely suited for investigating complex systems. Empirical vibrational spectroscopic maps are commonly employed to obtain the instantaneous vibration...

Recently, more attention have been paid on the construction of dipole moment functions (DMF) using theoretical methods. However, the computational methods to construct DMFs are not validated as much as those for potential energy surfaces do. In this letter, using Ar ⋯ He as an example, we tested how spectroscopy-accuracy DMFs can be constructed usi...

The quantitative prediction of vibrational spectra of chromophore molecules in solution is challenging and numerous methods have been developed. In this work, we present a quantum vibration perturbation (QVP) approach, which is a procedure that combines molecular quantum vibration and molecular dynamics with perturbation theory. In this framework,...

This work introduces a new permutation-symmetry-adapted machine learning diabatization procedure, termed the diabatization by equivariant neural network (DENN). In this approach, the permutation symmetric and anti-symmetric elements in diabatic potential energy metrics (DPEMs) were simultaneously simulated by equivariant neural network (ENN). The d...

High-dimensional potential energy surface (PES) for van der Waals systems with spectroscopic accuracy, is of great importance for quantum dynamics and an extremely challenge job. CO-N2 is a typical van der Waals system and its high-precision PES may help elucidate weak interaction mechanisms. Taking CO-N2 potential energies calculated by CCSD(T)-F1...

An ab initio intermolecular potential energy surface (PES) for the van der Waals complex of H2O–N2 that explicitly incorporates the intramolecular Q2 bending normal mode of the H2O monomer is presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory [CCSD(T)-F12] with an augmented cor...

We presented the first three-dimensional (3D) ab initio intermolecular potential energy surface (PES) for the H3O⁺–Ar complex. The electronic structure computations were carried out at the explicitly correlated coupled cluster theory-F12 with an augmented correlation-consistent triple zeta basis set. Analytic 3D PES was obtained by least-squares fi...

Tremendous interest in solid-state devices has prompted the development of descriptors that can be utilized to develop better materials. Previous work mostly focused on the static structure, while discovery of the interplay between cation mobility and anion dynamics can also provide a powerful descriptor. Here, we demonstrate that [PS4] rotation is...

Single-ion conducting solid electrolytes are gaining tremendous attention as essential materials for solid-state batteries, but a comprehensive understanding of the factors that dictate high ion mobility remains elusive. Here, for the first time, we use a combination of the Maximum Entropy Method analysis of room-temperature neutron powder diffract...

Helium (He4) nanodroplets provide a unique environment to observe the microscopic origins of superfluidity. The search for another superfluid substance has been an ongoing quest in the field of quantum fluids. Nearly two decades ago, experiments on doped parahydrogen (p−H2) clusters embedded in He4 droplets displayed anomalous spectroscopic signatu...

The rovibrational energy levels and intensities of the CH3F–H2 dimer have been obtained using our recent global intermolecular potential energy surface [X.-L. Zhang et al., J. Chem. Phys. 148, 124302 (2018)]. The Hamiltonian, basis set, and matrix elements are derived and given for a symmetric top-linear molecule complex. This approach to the gener...

We discuss here which of the dipole moment components of a linear triatomic molecule (of type A–B–A or A–B–C) will vanish, and which can be observed with non-zero values. We aim to resolve some confusion arisen in connection with the relationship between vibrationally averaged structures and the values of components of the electric dipole moment μ....

Molecular dynamics simulation of human heart lactate dehydrogenase (LDH) has been carried out to determine the linear and two-dimensional Fourier transform infrared (2D-FTIR) spectra for the carbonyl stretch vibration of pyruvate in the tetrameric enzyme, using quantum vibrational perturbation theory. The computed line-shapes of individual subunits...

Infrared (IR) spectroscopy, responding to molecular vibrations, is one of the most important tools in understanding the behavior of molecules. For complex systems, because of the relatively dense spectra lines, it could be very difficult to assign IR spectra merely by experience, an instance of which is non-bonded system. For middle-size system, th...

A first effective six-dimensional ab initio potential energy surface (PES) for CH3F–H2 which explicitly includes the intramolecular Q3 stretching normal mode of the CH3F monomer is presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster level of theory [CCSD(T)-F12a] with an augmented corr...

The calculated rovibrational energy levels and infrared spectra for OCS-(pH2)2, OCS-(oD2)2, OCS-(HD)2 and mixed OCS-pH2-He trimers are obtained by performing the exact basis-set calculations for the first time based on the newly developed potential energy surfaces (J. Chem. Phys. 2017, 147, 044313). The ``adiabatic-hindered-rotor'' (AHR) method is...

Spectroscopically accurate Potential Energy Surfaces (PESs) are fundamental for explaining and making predictions of the infrared and microwave spectra of van der Waals (vdW) complexes, and the model used for the potential energy function is critically important for providing accurate, robust and portable analytical PESs. The Morse/Long-Range (MLR)...

Interpreting high-resolution rovibrational spectra of weakly bound complexes commonly requires spectroscopic accuracy (<1 cm⁻¹) potential energy surfaces (PES). Constructing high-accuracy ab initio PES relies on the high-level electronic structure approaches and the accurate physical models to represent the potentials. The coupled cluster approache...

A thorough understanding of the intermolecular configurations of van der Waals complexes is a great challenge due to the weak interactions, floppy and anharmonic nature. Although high-resolution Microwave or Infrared...

An effective six-dimensional ab initio potential energy surface (PES) for H2–OCS which explicitly includes the intramolecular stretch normal modes of carbonyl sulfide (OCS) is presented. The electronic structure computations are carried out using the explicitly correlated coupled cluster [CCSD(T)-F12] method with the augmented correlation-consisten...

Morse/Long-Range potential energy model is a spectroscopically accurate model which has been expended to Multi-Dimension Morse/Long-Range (MD-MLR) model to describe the intermolecular interaction. In this work, we adopt the MD-MLR model to fit ab initio pointwise energies got from vibrationally averaging over the intramolecular vibrational coordina...

We describe a diabatic-at-construction (DAC) strategy for defining diabatic states to determine the adiabatic ground and excited electronic states and their potential energy surfaces using the multistate density functional theory (MSDFT). The DAC approach differs in two fundamental ways from the adiabatic-to-diabatic (ATD) procedures that transform...

Linear and two-dimensional infrared (IR) spectroscopy of site-specific probe molecules provides an opportunity to gain a molecular-level understanding of the local hydrogen-bonding network, conformational dynamics and long-range electrostatic interactions in condensed-phase and biological systems. A challenge in computation is to determine the time...

The assignment of the rovibrational spectra of molecule-Ne complexes is always a challenge to study van der Waals systems, since they usually exhibit behavior intermediate between free rotor and rigid rotor. In this paper, the microwave and infrared spectra of CH3F-Ne, a model system for symmetric-top-atom dimer, were firstly predicted and analyzed...

High resolution ro-vibrational transitions of the H2O-Ne complex in the bending region of H2O at 6 μm have been measured using a rapid scan infrared spectrometer based on an external cavity quantum cascade laser and an astigmatic multipass optical cell. To aid the spectral assignment, a four-dimension potential energy surface of H2O-Ne which depend...

A full-dimension intra- and inter-molecular ab initio potential energy surface (PES) for H2O-He, which explicitly incorporates dependence on the intra-molecular normal-mode coordinates of the H2O monomer has been calculated in this work. In addition, three analytic vibrational-quantum-state-specific PESs are obtained by least-squares fitting vibrat...

We provide the source code of our in-house program MoRiBS-PIMC. This program was developed to simulate rigid molecules rotating in bosonic clusters composed of helium atoms, parahydrogen molecules or any other bosonic point solvent particles. The program can be employed to obtain superfluid response, structural and energetic properties as well as i...

The origin and strength of intra- and inter-molecular vibrational coupling is difficult to probe by direct experimental observations. However, explicitly including or not including some specific intramolecular vibrational modes to study intermolecular interaction provides a precise theoretical way to examine the effects of anharmonic coupling betwe...

本文在从头算CCSD(T)/AVQZ水平上计算了CH 3 F-Ar体系包含CH 3 F分子 Q 3 振动的四维势能面. 以摩斯长程势(MLR)为模型, 分析的三维高精度分子间势能面通过非线性拟合振动平均的基态( n 3 =0)和激发态( n 3 =1)的能量而得到. 其中对2038个格点拟合的方差仅为0.08 cm -1 . 我们发现, 该体系相互作用能的主要贡献来源于短程的交换排斥能和长程的色散能, 势能面有3个极小值点, 在 q 方向表现出强烈的各向异性, 而在 j 方向各向异性比较弱. 与CH 3 F-He体系相比, 分子间相互作用较强，分子间相互作用对单个分子的束缚较明显, CH 3 F和Ar表现得更像紧束缚的超分子. 随后, 采用径向离散变量表象(DVR)和角度有限基组表象(FBR...

The idea of a macroscopic Andronikashvili experiment used to measure superfluid fraction of bulk liquid 4He can be ported into the realm of spectroscopic studies to measure the superfluid fraction of microscopic systems at the nanoscale. Theoretical studies are needed to fully unravel the superfluid information contained in such a microscopic Andro...

The microwave and infrared spectra of CO–(pH2)2, CO–(oD2)2, and CO–pH2–He trimers are predicted by performing exact bound state calculations on the global potential energy surfaces defined as the sum of accurately known two-body pH2–CO or oD2–CO (in Li et al. J Chem Phys 139:164315, 2013), pH2–pH2 or oD2–oD2 (in Patkowski et al. J Chem Phys 129:094...

The microwave and infrared spectra of CO–
(pH2)2, CO–(oD2)2, and CO–pH2–He trimers are predicted
by performing exact bound state calculations on the global
potential energy surfaces defined as the sum of accurately
known two-body pH2–CO or oD2–CO (in Li et al. J Chem
Phys 139:164315, 2013), pH2–pH2 or oD2–oD2 (in Patkowski
et al. J Chem Phys 129:09...

We report a first-principles prediction of the Raman shifts of parahydrogen (pH2) clusters of sizes N = 4-19 and 33, based on path integral ground-state simulations with an ab initio potential energy surface. The Raman shifts are calculated, using perturbation theory, as the average of the difference-potential energy surface between the potential e...

Four-dimensional ab initio intermolecular potential energy surfaces (PESs) for CH3F-He that explicitly incorporates dependence on the Q3 stretching normal mode of the CH3F molecule and are parametrically dependent on the other averaged intramolecular coordinates have been calculated. Analytical three-dimensional PESs for v3(CH3F) = 0 and 1 are obta...

A five-dimensional ab initio potential energy surface (PES) for CO-H2 that explicitly incorporates dependence on the stretch coordinate of the CO monomer has been calculated. Analytic four-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for vCO = 0 and 1 to the Morse/long-range potential function f...

An effective four-dimensional ab initio potential energy surface (PES) for He-OCS, which explicitly incorporates dependence on the intramolecular Q(1) (O-C) stretch normal mode of OCS and is parametrically dependent on its Q(3) (C-S) stretch coordinate has been calculated at the coupled-cluster single double triple/aug-cc-pVQZ level including bond...

We present the first simulation study of bosonic clusters doped with an asymmetric top molecule. The path-integral Monte Carlo method with the latest methodological advance in treating rigid-body rotation [Noya, E. G.; Vega, C.; McBride, C. J. Chem. Phys.2011, 134, 054117] is employed to study a para-water impurity in para-hydrogen clusters with up...

Direct observation of superfluid response in para-hydrogen (p-H2) remains a challenge because of the need for a probe that would not induce localization and a resultant reduction in superfluid fraction. Earlier work [ H. Li, R. J. Le Roy, P.-N. Roy and A. R. W. McKellar Phys. Rev. Lett. 105 133401 (2010)] has shown that carbon dioxide can probe the...

The vibration-rotation spectra of HBO and HBS have been investigated at
high resolution using a Fourier transform spectrometer. The HBO
molecules were produced in a high temperature furnace from the reaction
of H2O vapor with boron by heating a mixture of crystalline
boron and boron oxide (B2O3) at a temperature
˜1350°C. The spectra were recorded i...

We present an implementation of path integral molecular dynamics for sampling low temperature properties of doped helium clusters using Langevin dynamics. The robustness of the path integral Langevin equation and white-noise Langevin equation [M. Ceriotti, M. Parrinello, T. E. Markland, and D. E. Manolopoulos, J. Chem. Phys. 133, 124104 (2010)] sam...

We present the first simulation study of bosonic clusters doped with an
asymmetric top molecule. A variation of the path-integral Monte Carlo
method is developed to study a para-water (pH_2O) impurity in
para-hydrogen (pH_2) clusters. The growth pattern of the doped clusters
is similar in nature to that of the pure clusters. The pH_2O molecule
appe...

Inspired by a recent successful adiabatic-hindered-rotor treatment for parahydrogen pH(2) in CO(2)-H(2) complexes [H. Li, P.-N. Roy, and R. J. Le Roy, J. Chem. Phys. 133, 104305 (2010); H. Li, R. J. Le Roy, P.-N. Roy, and A. R. W. McKellar, Phys. Rev. Lett. 105, 133401 (2010)], we apply the same approximation to the more challenging H(2)O-H(2) syst...

The infrared spectrum of CO(2)-(pH(2))(2) trimers is predicted by performing exact basis-set calculations on a global potential energy surface defined as the sum of accurately known two-body pH(2)-CO(2) (J. Chem. Phys. 2010, 132, 214309) and pH(2)-pH(2) potentials (J. Chem. Phys. 2008, 129, 094304). These results are compared with new spectroscopic...

Water-hydrogen clusters are of considerable interest for both fundamental and practical reasons; in particular, a better understanding of their nature has implications in astrophysics and in the field of hydrogen storage. The present research investigates the quantum dynamics of water-hydrogen clusters based on a new interaction potential, exact bo...

Clusters of p-H_2 had been predicted to exhibit superfluid behavior twenty years ago, but direct observation of this phenomenon was elusive until our recent work combining experimental measurments and theoretical simulations of the non-classical rotational inertia and superfluid response of p-H_2 clusters doped with CO_2. However, the size-dependen...

The recently introduced [Mol. Phys. 105, 663 (2007)] ‘Morse/long-range’ (or MLR) potential energy function is a very flexible form which explicitly incorporates the theoretically predicted inverse-power-sum long-range tail, is smooth and differentiable everywhere, and includes the well depth , equilibrium distance re, and long-range interaction coe...

The rovibrational energy levels (J = 0-3) and rotational spectra of seven isotopologues of the OCS-(He)(2) complex have been determined by numerically exact basis set calculations. The interaction energy is represented as a sum of two-body terms consisting of the OCS- He potential, which Howson and Hutson (J. Chem. Phys. 2001, 115, 5059) obtained a...

In para-H(2)-{molecule} interactions, the common assumption that para-H(2) may be treated as a spherical particle is often substantially in error. For example, quantum mechanical eigenvalues on a full four-dimensional (4D) potential energy surface for para H(2)-{linear molecule} species often differ substantially from those calculated from the corr...

Clusters of para-hydrogen (pH₂) have been predicted to exhibit superfluid behavior, but direct observation of this phenomenon has been elusive. Combining experiments and theoretical simulations, we have determined the size evolution of the superfluid response of pH₂ clusters doped with carbon dioxide (CO₂). Reduction of the effective inertia is obs...

Five-dimensional ab initio potential energy surfaces (PESs) for CO(2)-H(2) that explicitly incorporate dependence on the Q(3) asymmetric-stretch normal-mode coordinate of the CO(2) monomer and are parametrically dependent on its Q(1) symmetric-stretch coordinate have been calculated. Analytic four-dimensional PESs are obtained by least-squares fitt...

The infrared spectra of several isotopologues of the CO_2-(para-H_2)_2 trimer have been predicted by applying exact basis-set calculations to a global potential energy surface which is defined as a sum of the accurately known two-body para-H_2--CO_2 and para-H_2--para-H_2 potentials. These results are compared with new spectroscopic measurements, f...

High resolution infrared spectra of an N_2O molecule seeded in ultra-cold helium clusters have been reported by two groups. Early simulations of N_2O--(He)_n clusters were performed using potential energy surfaces (PESs) for which the dopant N_2O molecule was frozen at its equilibrium geometry. Since the evolution of the shift of the nu_3 band-orig...

The prospect of directly observing superfluidity in para-H_2 is a
tantalizing but elusive goal. Like ^4He, para-H_2 is a light zero-spin
boson. However, H_2-H_2 intermolecular interactions, though weak, are
stronger than He-He interactions, and hydrogen is a solid below about 14
K. This makes detection of superfluidity in bulk hydrogen problematica...

Since para-H_2 molecules are spin zero bosons (like ^4He atoms) they
might also show superfluid behavior at low temperatures. Results of
recent spectroscopic studies of molecules embedded in helium droplets
suggests that a new route for investigating superfluidity of
para-hydrogen (p-H_2) would be to consider p-H_2 clusters doped with a
single chro...

Numerical calculations show that four modern potential energy surfaces for N(2)-He all support 18 bound intermolecular states for the homonuclear isotopologues (14,14)N(2)-(4)He and (15,15)N(2)-(4)He, and 12 (or 13, for one surface) truly bound states for (14,15)N(2)-He. This contradicts a recent statement [Patel et al., J. Chem. Phys. 119, 909 (20...

Observations of the rotational lines of HCO$^+$ produced in an extended negative glow discharge revealed high vibrational temperatures for the stretching vibrational modes, and non-thermal population distributions among the different $\ell$ levels of excited bending vibrational states., \textbf{127},074301 (2007).}$^{,}$, \textbf{248}, 26 (2008).}...

Spectroscopic studies of molecules embedded in helium droplets provide a unique opportunity to investigate a superfluid. High-resolution infrared spectra of CO$_2$-(He)$_N$ clusters ranging in size from `small' ($N\!\simeq \!1-17$) to `intermediate' ($N\!\sim 60$) have been reported recently by McKellar and co-workers.\ {\bf 92}, 145503 (2004);~ A....

Path-integral Monte Carlo simulations of the nu(3) vibrational band origin frequency shifts of CO(2) in (He)(n) clusters for n=1-40 show that although only the asymmetric-stretch mode of CO(2) is being excited, the effect of the associated change in the average value of Q(1) cannot be ignored. When this fourth degree of freedom is taken into accoun...

To obtain theoretical insight regarding the stability and formation dynamics of the interstellar ions HCO(+) and HOC(+), stationary points and the associated vibrational frequencies on the full nine-dimensional potential energy surface for the electronic ground state have been calculated using coupled-cluster theory with both single and double subs...

A three-dimensional, analytic potential energy surface for CO(2)-He that explicitly incorporates its dependence on the Q(3) asymmetric-stretch normal-mode coordinate of the CO(2) monomer has been obtained by least-squares fitting new ab initio interaction energies to a new three-dimensional Morse/Long-Range (3D-MLR) potential function form. This fi...

In this study, a new calibration method, standard-free kinetic calibration, is proposed for rapid on-site analysis by solid-phase microextraction (SPME), based on the diffusion-controlled mass transfer model and equilibrium extraction. With this calibration method, all analytes can be directly calibrated with only two samplings. The feasibility of...

High resolution infrared spectra of (He)$_N$-CO$_2$ clusters with $N$ up to 60 have been studied by McKellar and co-workers, in the region of the $\nu_3$ fundamental band of CO$_2$.} {\bf 92}, 145503 (2004); ~A.R.W.\ McKellar, {\em J.\ Chem.\ Phys.} {\bf 128}, 044308 (2008).}~ By fitting to the rotation-vibration transitions for each cluster size,...

To provide insight regarding the stability of the interstellar ions HCO$^+$ and HOC$^+$, the geometries and frequencies of the stationary points (transition state, reactants, intermediates, and products) on the ground potential energy surface of the CO+H$_3^+$ system have been calculated using coupled-cluster theory with both single and double subs...

A three-dimensional potential energy surface for the ground electronic state of MgH2 has been constructed from 9030 symmetry-unique ab initio points calculated using the icMRCI+Q method with aug-cc-pVnZ basis sets for n=3, 4, and 5, with core-electron correlation calculated at the MR-ACPF level of theory using cc-pCVnZ basis sets, with both calcula...